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INSTALLATION
A
IGNITION NOISE INTERFERENCE
Use of a mobile receiver at low signal levels is normally limited by the presence of
electrical noise. The primary source of noise in automobile installation is from the
generator and ignition system in the vehicle. Under most operating conditions, when
signal level is adequate, the background noise does not present a serious problem. Also,
when extremely low level signals are being received, the transceiver may be operated with
vehicles engine turned off. The unit requires very little current and therefore will not
significantly discharge the vehicle battery.
Even though the transceiver has ANL and NB controls, in some installation ignition
interference may be high enough to make good communications impossible. The electrical
noise may come from several sources. Many possibilities exist, as variations between
vehicles require different solutions to reduce the noise.
ANTENNA
A vertically polarized, quarter-wavelength whip antenna provides the most reliable
operation and greatest range. Shorter, loaded-type whip antennas are more attractive,
compact and adequate for applications where the maximum possible distance is not
required. Also, loaded whips do not present the problems of high wind resistant imposed
by a full quarter-wavelength whip.
Mobile whip antennas utilize the metal body of the vehicle as a ground plane. When
mounted at a corner of the vehicle they are slightly directional, in the direction of the body
of the vehicle. For all practical purpose, however, the radiation pattern is nondirectional.
The slight directional characteristic will be observed only at extreme distances. A standard
antenna connector (type SO-239) is provided on the transceiver for easy connection to a
standard PL-259 cable termination.
If the transceiver is not mounted on a metal surface, it is necessary to run a separate
ground wire from the unit to good metal electrical ground in the vehicle. When installed in
a boat, the transceiver will not operate at maximum efficiency without a ground plate,
unless the vessel has a steel hull.
Before installing the transceiver in a boat, consult your dealer for information regarding
an adequate grounding system and prevention of electrolysis between fittings in the hull
and water.
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INSTALLATION
A
TUNING THE ANTENNA FOR OPTIMUM S.W.R
Since there is such a wide variety of base and mobile antennas, this section will strictly
concern itself to the various types of mobile adjustable antennas.
Because the antenna length is directly related to the channel frequency, it must be tuned
to resonate optimally on all channels of the transceiver. Channel 1 requires a longer
antenna than Channel 40 because it is lower in its frequency of operation.
Due to the various methods of adjusting antennas for proper S.W.R. we have chosen
what we think is the optimum method:
A.
Antenna with adjustment screws (set screws).
1.
Starts with the antenna extended and tighten the set screw lightly enough so that the
antenna can be lightly tapped with your finger for easy adjustment.
2.
Set your transceiver to Channel 20. Press the PTT (push-to-talk) switch, and tap the
antenna (making it shorter). The S.W.R meter will show a lower reading each time the
antenna is tapped. By continuing to shorten the antenna, you will notice the S.W.R
reading will reach a low point and then start rising again. This means that you have
passed the optimum point for Channel 20.
Extend the antenna a short distance and again follow the procedure above. When the
lowest point has been reached, switch to Channel 1 and then to Channel 40 and compare
S.W.R readings. They should be almost equal.
NOTE
The proper setting is achieved when the SWR is 1.5 or
below, and when it has the same reading for channels 1
and 40.
B.
Antennas which must be cut to proper length
1.
Follow the same procedure as above but adjust the length by cutting in 1/8”
increments until a good match is obtained.
2.
Be very careful not to cut too much at one time, as one it is cut, it can no longer be
lengthed.
3.
The whip is easily cut by filing a notch all the way around and breaking the piece off
with pliers.